If there is a sapling here, it means that someone was able to gather some parts of the main tree of life. Even if the tree is still lost, or believed to be lost, at least there is a way to grow a new tree with the saplings.
The question quickly becomes how would Evan be able to grow the tree while also keeping it hidden.
He's getting the sapling from this cave because it doesn't have the space it needs for it to grow. Not to mention that it can be used as a material, something he didn't know until Iva mentioned it.
Didn't change the fact that the sapling of life is his now. But he needs to find more about the tree of life soon.
Evan stretched his limbs a little bit. "Do you have any idea why its here?"
"Not really. I don't have any clue." Iva replies. "Users before you never saw the tree of life and I haven't either."
Evan sighs. "Fair enough. Looks like it's mine until I found out a way to make it grow and make more saplings."